Ee re 
COMPLEX STRESS DISTRIBUTIONS IN ENGINEERING MATERIALS. 193 
qualitative only ; it certainly detects brittleness, which the Wéhler test 
does not; but whether it can give a quality factor which, besides excluding 
brittleness, includes resistance to repeated stresses of very small overstrain, 
is a matter quite unproved. 
(3) Method suggested by Bauschinger and latterly investigated by 
Bairstow (No. 2), viz., a very few repetitions of alternate overstrain and 
heating to 100° C. This has not been advanced as a quick method for 
finding the elastic ranges ; indeed, further experiment is required. If the 
method should prove satisfactory for certain classes of steel only, it would 
seem to be worth while to design special apparatus for carrying out 
expeditiously the present rather cumbersome process. 
Should (1) or (3) be adopted means would have to be taken to discover 
impurities and flaws, since these, which. vastly imit the endurance, would 
not be detected. 
Materials other than Wrought Iron and Steel. 
The information concerning the resistance of materials other than 
wrought iron and steel is not extensive ; what the writer has found may be 
consulted by the aid of the following references :— 
Cast Iron. 
No. 59. Alternate direct stress, 
No. 93. Repeated bending in one 
direction (see Unwin’s 
‘Testing of Materials ’). 
[xe 23. Alternate + and — bending. 
Endurance tests 
Elasticity and pic naa 
under repeated loading, | Nos. 8 and 9. 
&e. . ; - Aye 
Copper. 
Endurance tests . . ah oe Alternate + and — bending. 
No. 24. Alternate combined stress 
(with considerable over- 
strain). 
Suggestions for Research. 
The writer understands that the following researches are in progress :— 
High-speed tests on resistance at temperatures of 100° C. and other 
temperatures. 
Experiments on elastic hysteresis on a high-speed direct-stress machine. 
Experiments on alternating combined stress. 
Experiments on the effect on resistance of keyways, &c. 
The following suggestions for further research seem worthy of con- 
sideration :— 
(1) That experiments be made at 0° C. with unequal + stresses, in 
order to study the effect of recovery and adjustment of the elastic hmits 
at that temperature. 
(2) That (as suggested by L. Bairstow, No. 2) experiments be made to 
determine the ‘ permanent extension,’ if any, when the range of stress 
(direct) is less than the safe range. 
(3) That the validity of the method of finding the safe elastic ranges by 
1913. Oo 
